Bent axis hydrostatic module with multiple yokes

ABSTRACT

A bent axis hydrostatic module, comprising: a frame, a pair of parallel laterally spaced shafts rotatably supported by the frame and directed outwardly from the frame in the same direction. Two yokes are pivotally mounted about parallel axes on the frame. A hydrostatic power unit is swingably carried by each yoke, and each hydrostatic power unit being operatively connected to one of the shafts to rotate the same. A pair of system pressure conduits in the frame with each of the pressure conduits are fluidly connected to each of the cylinder blocks. A control system is provided for pivoting the yokes including means for independently pivoting the yokes about parallel axes.

CROSS REFERENCE TO A RELATED APPLICATION

This application claims the benefit of Applicants' ProvisionalApplication Ser. No. 60/483,222 filed Jun. 27, 2003.

BACKGROUND OF THE INVENTION

The present invention relates to the field of variable displacement bentaxis hydraulic units. Bent axis hydraulic units have been known for manyyears.

Such devices obviously have power output limited to their physical size.When additional power is required, a solution is to provide a unit oflarger size. However, space and size become a problem in certain vehicledesigns and serve to prevent larger bent axis hydraulic units fromaccommodating this situation when more power and limited space arespecified.

Prior art shows attempts to use hydromodules that have multiple yokes;however, these inventions fallen short when attempting to provide ahydromodule with bent axis hydrostatic units that have a simplifiedconstruction with as few parts as necessary, as well as a compactconstruction with the yokes taking up as little space as possible. Forexample, the U.S. Pat. No. 6,530,855 patent to Folsom discloses bentaxis hydrostatic modules that have multiple yokes. When referring toWO99/24738 as referred to by Folsom, one can see Folsom relies on astationary manifold block to accommodate its fluid passages between thepump and the motor, with the porting of hydrostatic flow through thepiston slippers to the cylinder block. Thus, the Folsom patent shows asizeable construction with a large number of separate parts whichpotentially results in a higher unit manufacturing cost as well aspotential decreases in the unit's reliability.

It is therefore a principal object of this invention to provide a bentaxis hydrostatic unit with a pair of bent axis hydrostatic power unitsworking in unison in side by side relation to provide a greater poweroutput, and which includes parallel, unidirectional rotatable powershafts; dual swingable yokes pivotally mounted on a frame, and means forindependently pivoting the yokes about parallel axes.

It is a further object of the invention to provide a bent axishydrostatic module with multiple yokes wherein the yokes are of singlepiece construction.

It is another object of the invention to provide a bent axis hydrostaticmodule with multiple yokes wherein the yokes contain integrated fluidpassages.

These and other objects, features, or advantages of the presentinvention will become apparent from the specification and claims.

BRIEF SUMMARY OF THE INVENTION

A hydrostatic module is disclosed, including a pair of parallellaterally spaced shafts rotatably supported by a frame, and directedoutwardly from the frame in the same direction. Two single piece yokescontaining integrated fluid passages are pivotally mounted aboutparallel axes on the frame. A hydrostatic power unit is swingablycarried by each yoke, and each hydrostatic power unit is operativelyconnected to one of the shafts to rotate the same. A pair of systempressure conduits are located in the frame, with each of the pressureconduits being fluidly connected to each of the cylinder blocks. Acontrol system independently pivots the yokes about parallel axes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of an embodiment of the hydrostaticmodule of the present invention;

FIG. 2 is a back perspective view of the hydrostatic module of thepresent invention;

FIG. 3 is a perspective view of the control housing of the presentinvention;

FIG. 4 is a cross sectional top view of the hydrostatic module of thisinvention;

FIG. 5 is a schematic top view of the yokes and stops of the presentinvention;

FIG. 6 is a partial a cross sectional side view of the hydrostaticmodule of this invention;

FIG. 7 is a top view of the porting plate of the present invention; and

FIG. 8 is a front perspective view the hydrostatic module of the presentinvention showing a joint surface of the manifold.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the hydrostatic module 10 of the present inventionincludes bent axis hydrostatic units 11 and a frame 12. The frame 12acts as a structural unit to hold and locate other components, and alsoreacts against forces within module to hold components in place.

Referring to FIG. 4, a clutch unit yoke 14 and ring unit yoke 16 containand carry hydrostatic power units (cylinder blocks or kits) 23 and 24,respectively, and are pivotally mounted on the frame 12 to pivot withrespect to the frame 12 in intersecting paths. The two yokes 14 and 16are captured between the frame 12 and a manifold 22, when assembled.

The hydrostatic power units 23 and 24 are operatively connected to apair of parallel laterally spaced shafts 25 and 26, respectively. Theshafts 25 and 26 are rotatably supported by the frame 12 and directedoutwardly from the frame 12 in the same direction. The hydrostatic powerunits 23 and 24 operate to rotate the shafts 25 and 26.

The two hydrostatic power units 23 and 24 are then contained within, andloaded against, the yokes 14 and 16 and the frame 12. The frame 12positions the shafts 25 and 26 in turn aligns gears 27 assembled to theshafts 25 and 26 within the planetary ring gear and clutch gear of avehicle transmission (not shown) respectively. Thus, the two hydrostaticpower units 23 and 24 and the associated yokes 14 and 16 are referred toas the clutch unit yoke 14 and ringed unit yoke 16.

Referring to FIG. 6, the yokes 14 and 16 are preferably of single piececonstruction. These single piece yokes 14 and 16 contain integratedfluid passages 28 and 30. Details of single piece yokes 14 and 16containing integrated fluid passages 28 and 30 are disclosed in U.S.Pat. No. 6,203,283, which is hereby specifically incorporated herein byreference in its entirety.

The manifold 22 functions as the conduit for high pressure fluid betweenall hydrostatic power units 23 and 24 in the assembly and also containsthe necessary valving for the hydromodule 10. The manifold 22 hasauxiliary valving (not shown) for pressure protection and loop flushing.The manifold 22 also has two internal cored passages 32 and 34 extendingfrom yoke 14 to yoke 16 to form two working loops of the hydromodule 10,These internal cored passages 32 and 34 act as a conduit to channel oilfrom one yoke to the other.

The passages 32 and 34 in manifold 22 port fluid through the integratedfluid passages 28 and 30 of yoke 16. The passages 32 and 34 communicatewith integrated fluid passages 28 and 30 along the trunnion 36 of theyoke 16. The fluid is transported through one of the integrated fluidpassages 28 and 30 in yoke 16 from the trunnion 36 to an end wall 38B.In the end wall 38B the fluid is pulled from one of the integrated fluidpassages 28 and 30 into one side of the hydrostatic power unit 24. Theother side of the hydrostatic power unit 24 forces fluid back into theother of the integrated fluid passages 28 and 30 at the end wall 38B,and from there back to trunnion 36 and the corresponding integratedfluid passage 28 or 30. Likewise, yoke 14 includes a similar integratedfluid passage structure.

As shown in FIG. 4, each yoke 14 and 16 has outer surface 40A and 40Bincluding end wall 38A and 38B and a side wall 42A and 42B,respectively. The outer surfaces 40A and 40B of yokes 14 and 16 havecomplimentary surfaces to one another as well as to the frame 12 tominimize the magnitude of the space occupied by the yokes 14 and 16 whenthe complimentary surfaces of outer surfaces 40A and 40B are in closelyspaced relation.

Specifically, the end wall 38A of yoke 14 includes a contoured portion44A on the yoke 14 outer surface 40A. This contoured portion 44A permitsthe end wall 38A of yoke 14 to be nested or positioned in closely spacedrelation to the side wall 38B of the yoke 16 without the two yokes 14and 16 contacting one another. Likewise a contour rib 46 on the frame 12is contoured to mate with the yoke 14 side wall 42A.

The contour angle on these portions 44A and 46 is a function of thepivot angle of the yokes 14 and 16. The yoke 14 pivots counter clockwisethrough an angle theta (θ) and the yoke 16 pivots clockwise through anangle alpha (α). (FIG. 4). Specifically, the yoke 14 has a yokecenterline B that pivots counter clockwise through an angle θ relativeto a shaft 25 centerline A. Yoke 16 has a yoke centerline C that pivotsclockwise through an angle α relative to a shaft 26 centerline D of thatyoke. Consequently the angle of the contour portion 44A on the end wall38A of the yoke 14 is equal to θ plus α relative to the centerline B ofthe yoke 14. Likewise, the angle of the contour rib 46 on the frame 12mating with the side wall 42A of the yoke 14 is equal to 90 degreesminus θ, relative to a surface E of the frame 12 perpendicular to theshaft 25 centerline A.

The provision of portions 44A and 46 allows the width dimension of thehydrostatic module 10 to be minimized, where the width dimension of thehydrostatic module 10 is a critical design criteria. Specifically, thehydromodule 10 of this invention is intended to fit within the housingenvelope of modern tractors which are compact and need to avoidinterference with the line of sight visibility of the operator who mustclearly see the ground surface immediately in front of the cab. Further,the position of the yokes 14 and 16 must meet the requirements ofgearing center lines, including alignment of shafts 25 and 26 with gearcenter lines while allowing the yokes 14 and 16 to be positioned closertogether without interference with each other. Additionally, each yoke14 and 16 must be able to be placed at multiple angular positionsregardless of the position of the other yoke. Thus, minimizing the widthdimension of the hydrostatic module 10 is a critical design criteriawhich the portions 44A and 46 permit.

As shown in FIG. 5, the hydromodule 10 is provided with more than 2 hardstops. Typically with a variable angle yoke, there are two mechanicalhard stops that limit the travel of the yoke. In the present invention,the provision of more than 2 hard stops allows the yokes 14 and 16 to beaccurately positioned at an angle between the two mechanical hard stops.

Specifically, the hydromodule 10 incorporates four stops 50, 52, 54, and56 into frame 12 to stop the yokes 14 and 16, which swing in closeproximity to each other, from coming into contact. The hydromodule 10has a clutch unit yoke 14 max outboard angle stop 50 and inboard anglestop 52. The ring unit yoke 16 has a yoke max inboard angle stop 54 andoutboard angle stop 56. The stops 50, 52, 54, and 56 may be of anysuitable angle. The yokes 14 and 16 define a neutral position for thecylinder blocks 23 and 24 and the shafts 25 and 26 when in predeterminedpositions of pivotal movement (shaft 25 centerline A and shaft 26centerline D). The stops 50, 52, 54, and 56 permit the yokes 14 and 16to be pivoted within the following parameters with “plus” meaning aclockwise direction from a neutral position, and “minus” meaning acounterclockwise direction from a neutral position. As shown, the clutchunit yoke 14 swings through an arc of a minimum angle of −45° at stop 50to a maximum of +45° at stop 52. The ring unit yoke 16 swings through anarc minimum angle of −15° at stop 54 to a maximum angle of +45° at stop56. Thus stops 50, 52, 54, and 56 permit the yokes 14 and 16 to bepivoted to the following combination of positions: one yoke minus 45°and one yoke minus 15°; one yoke plus 45° and one yoke minus 15°; oneyoke plus 45° and one yoke minus 15°; one yoke plus 45° and one yokeplus 45°; one yoke minus 45° and one yoke minus 45°; and one yoke 45°and one yoke at 15°.

An integral stop 58 on yoke 16 and a corresponding integral groove 60 onyoke 14 are physical features incorporated into the two hydrostaticyokes 14 and 16. As the hydrostatic yokes 14 and 16 swing through arange angles in close proximity to each other, the integral stop 58 onyoke 16 provides additional angles where the yokes 14 and 16 can bestopped at a known position. The integral stop 58 on yoke 16 and thecorresponding integral groove 60 on yoke 14 are placed on the yokes 14and 16 such that they come into contact at the desired combination ofangles.

The additional combinations yoke angles set by the integral stop 58 andintegral groove 60 are needed to more accurately set the hydrostaticratio of the hydromodule 10. The yokes 14 and 16 are hydraulicallypositioned with a position sensing servo control system 62 (shown inFIGS. 1 and 3). The integral stop 58 and integral groove 60 are neededat special combinations of yoke angles because the servo control system62 does not offer the accuracy and repeatability that an integral stop58 provides. This combination of angles can be at any desired angleother than the minimum and maximum stop limits. As shown, integral stop58 on yoke 16 and the corresponding integral groove 60 on yoke 14 wereadded to the yokes 14 and 16 to create physical interference between theyokes 14 and 16 at a specific combinations of yoke angles where the leftyoke 14 is commanded to a physical hard stop at +44.5° and the rightyoke 16 is commanded to a physical hard stop at +13.5°.

As shown in FIGS. 1 and 3, the servo control system 62 of hydromodule 10includes a single piece control housing 64. The control housing 64contains the hardware required to control the positions of the yokes 14and 16, and thus the displacement of the hydrostatic power units 23 and24—as commanded by an operator.

Specifically, the single piece control housing 64 is specially equippedwith a first servo control 67 including a first servo valve 70 that isassociated with a first servo piston 68 and a first bias piston 72. Thehousing 64 likewise has a second servo control 73 including a secondservo valve 76 that is associated with a second servo piston 74 andsecond bias piston 78. The servo valves 70 and 76 control the hydraulicpressure on servo pistons 68 and 74 as well as bias pistons 72 and 78.The hydraulic pressure on pistons 68, 74, 72, and 78 causes the pistons68, 74, 72, and 78 to slide in and out of the single piece controlhousing 64. As best seen in FIG. 6, the second servo control 73 positionthe yoke 16 by the pistons 74 and 78 rotating the trunnion 36 as thepistons 74 and 78 slide in and out of the single piece control housing64. Likewise, first servo control 67 pistons 68 and 72 act in a similarmanner to position the yoke 14. Thus, the multiple servo controls 67 and73 independently establish the position of the hydrostatic yokes 14 and16 and the rotational power supplied to the shafts 25 and 26 over anoperating range of +/−45°.

As shown in FIGS. 1, 3 and 7, the servo control system 62 of hydromodule10 includes a control porting plate 66 attached to the single piececontrol housing 64. The control system 62 routes oil to the multipleservo controls 67 and 73 and makes a plurality of hydraulic connectionsbetween a transmission (not shown) and the hydromodule 10 inside thetransmission. One of the plurality of hydraulic connections between atransmission (not shown) and the hydromodule 10 is placed in the controlporting plate 66. The remaining hydraulic connections between atransmission (not shown) and the hydromodule 10 are placed in the singlepiece control housing 64.

Specifically, the control porting plate 66 has a single control supplypressure inlet 80. The single control supply pressure inlet 80 ishydraulically connected to a transmission (not shown) to receivehydraulic fluid. The control porting plate 66 routes the hydraulic fluidfrom the single control supply pressure inlet 80 to multiple outletgroves 82A-E. These outlet grooves 82A-E are positioned to abut thesingle piece control housing 64. These outlet groves 82A-E hydraulicallycommunicate with corresponding inlets (not shown) to the multiple servocontrols 67 and 73, to supply hydraulic pressure to the variouscomponents of the multiple servo controls 67 and 73. Thus, the controlporting plate 66 acts as a manifold to route the hydraulic fluid tomultiple locations within the single piece control housing 64.

Additionally, as noted above, the single piece control housing 64 has amultiple hydraulic connections between a transmission (not shown) andthe hydromodule 10. These multiple hydraulic connections include ahydromodule loop charge pressure supply 88, a first pressure commandsignal outlet 90, a second pressure command signal outlet 92, and ahydromodule loop cooling flow return 94. These multiple hydraulicconnections 88, 90, 92, and 94 route the hydraulic fluid to multiplelocations within the manifold 22 as well as the yokes 14 and 16.

Thus, the control housing 64 includes the integration of fluid passages,support structure, servo valves, and servo pistons into a single pieceto control multiple hydrostatic yokes 14 and 16. The fluid passages,support structure, servo valves, and servo pistons are all packaged intothe single housing 64 to fit into limited space provided inside anagricultural tractor transmission (not shown). The control housing 64design is a variation of the SINGLE-PIECE PROPORTIONAL CONRTOL designdisclosed in U.S. Pat. No. 6,260,468, the disclosure and drawings ofwhich are hereby specifically incorporated herein by reference in itsentirety.

As shown in FIGS. 1 and 2, a joint surface 100 on the manifold 22 matesthe manifold 22 to the control housing 64. As shown in FIGS. 3 and 8,mounting feature pegs 102 extend from joint surface 100. The mountingfeature pegs 102 mate with corresponding mounting feature holes 104 inthe control housing 64. The corresponding mounting feature pegs andholes 102 and 104 properly position the control housing 64 with respectto the manifold 22 during assembly. Likewise bolt holes 106 in jointsurface 100 and the control housing 64 align with one another to permitthe control housing to be removably affixed to the manifold 22.

Additionally, still referring to FIGS. 3 and 8, control housing ports108 align with manifold ports 110 on the joint surface 100. The controlhousing ports 108 route fluid between the hydromodule loop chargepressure supply 88 and the hydromodule loop cooling flow return 94 tothe manifold ports 110 on the joint surface 100. The manifold ports 110operate as fluid valving to route fluid between internal cored passages32 and 34 in the manifold 22 which act as a conduit to channel oil fromone yoke to the other and port fluid through the integrated fluidpassages 28 and 30 of yokes 14 and 16. Thus, the hydraulic system flowbetween vehicle and module 10 is routed to the manifold 22 through thecontrol housing 64, improving the exchange of fluid at the controlhousing 64 and manifold joint 100. The close proximity of the controlhousing 64 to the manifold 22 allows for simplified exchange ofhydraulic fluids required for the function of the module 10, allowingfor a more compact design and thus benefiting packaging as well as cost.

Additionally, due to the joining of the control housing 64 to themanifold 22 at joint surface 100, the control housing 64 shares in thecharacteristics of the manifold 22. The manifold 22 is a main structuralelement of the module 10 and is designed to be located very exactly toall key hydromodule 10 components. The manifold 22 is stiff and rigidand maintains its position and space as large loads act upon it. Themanifold 22 is also used as a structural support component for theleveraged stiffness required to react to the forces created in thecontrol housing 64. The stiffness of the control housing 64/manifold 22allows the use of mounting features 102 and 104 for manifold 22 to beadded to the control housing 64. Thus, the forces acting on the controlhousing 64 are shared through the joint 100 by the rest of thehydromodule 10 structure.

Therefore, disclosed is a bent axis hydrostatic module 10 with multipleyokes 14 and 16 which are shaped and positioned to nest with each otherso as to minimize the space requirement of the entire hydrostatic module10. The invention also provides a bent axis hydrostatic module 10 withmultiple yokes 14 and 16 wherein mechanical stops 58 and 60 are providedon the yokes 14 and 16 to control the pivoting angle of the yokes 14 and16. In addition, the invention also provides a bent axis hydrostaticmodule 10 with multiple yokes 14 and 16 wherein a single piece controlhousing 64 is provided to control the movement of both yokes 14 and 16.Further, the invention also provides a hydrostatic module 10 with astiff structural fluid manifold 22 assembly secured to the controlhousing 64. Finally, the invention also provides a hydrostatic module 10with a single piece porting plate 66 to convey fluid to the neededlocations within the control housing 64.

It will be appreciated by those skilled in the art that other variousmodifications could be made to the device without the parting from thespirit in scope of this invention. All such modifications and changesfall within the scope of the claims and are intended to be coveredthereby.

1. A bent axis hydrostatic module, comprising: a frame; a pair ofparallel laterally spaced shafts rotatably supported by the frame anddirected outwardly from the frame in the same direction; two yokespivotally mounted about parallel axes on the frame; a hydrostatic powerunit swingably carried by each yoke, and each hydrostatic power unitbeing operatively connected to one of the shafts to rotate the same; apair of system pressure conduits in the frame with each of the pressureconduits being fluidly connected to each of the cylinder blocks; and acontrol system for pivoting the yokes including means for independentlypivoting the yokes about parallel axes.
 2. The hydrostatic module ofclaim 1, wherein the yokes are of single piece construction. 3.Thehydrostatic module of claim 1, wherein the yokes contain integratedfluid passages.
 4. A bent axis hydrostatic module, comprising: a frame;a pair of parallel laterally spaced shafts rotatably supported by theframe and directed outwardly from the frame in the same direction; twoyokes pivotally mounted about parallel axes on the frame, wherein theyokes are of single piece construction and contain integrated fluidpassages; a hydrostatic power unit swingably carried by each yoke, andeach hydrostatic power unit being operatively connected to one of theshafts to rotate the same; a pair of system pressure conduits in theframe with each of the pressure conduits being fluidly connected to eachof the cylinder blocks; and a control system for pivoting the yokesincluding means for independently pivoting the yokes about parallelaxes.